This invention relates to a calibration technique for setting the switching characteristics of an electromagnetic relay of the type including at least one flat pole plate and an armature that is resilient, or resiliently mounted, and that opposes the pole plate with overlapping pole faces while leaving a prescribed air gap are accomodated in a housing. The present invention also relates to a relay having a construction that can be readily calibrated.
In relays with a resiliently mounted armature, it is usually necessary to control adjustably the spring force exerted on the armature by bending the spring in order to obtain the desired relay characteristics, usually the voltage levels at which the relay responds or falls off, that is, within a desired range and hence compensate for every possible deviation in manufacturing tolerance. Bending an armature-restoration spring, however, is not only expensive but will also permanently change the spring properties, which can for example affect the life of the relay.
When, on the other hand, the armature simultaneously serves as a contact element, as in the case with reed contacts, the response levels can be adjusted only to a limited extent by bending the armature because bending also changes the inter-contact distance, with accordingly undesirable results. If the armature and pole plate also happen to be accommodated in a closed contact space, bending adjustment is in any case only possible with specific designs and by specific methods. Thus, with a multiple contact of the type disclosed in German Patent Document OS No. 2 059 390, the armature and its bearing spring are no longer accessible once the contact space has been closed. It is, however, only after the contact has been manufactured and inserted into a relay that response and extinction levels can be controlled and evaluated sufficiently to compensate for deviations in manufacturing tolerances.